Rubin has been at the Club since the age of eight, and made his First Team debut for the Bluebirds on February 13th, 2021 as a substitute in a 3-1 victory against Coventry City at CCS.

The attacker went on to make six appearances for City in 2020/21 and his breakout season was rewarded with a first U21 call-up for Wales. He would subsequently be called into the EURO 2020 training group by Rob Page, before being selected in the final 26-man squad for the tournament.

Rubin scored six goals for City during the 2021/22 season and registered his first international strike in a 1-1 draw with Czech Republic on March 30th, 2022. He also featured for Wales in the 2022 FIFA World Cup in Qatar.

Colwill played 40 times for the Bluebirds in 2023/24, and made his 100th appearance for the club in a 1-0 home win over Huddersfield Town in March 2024.

The Academy graduate was named Vice Captain to Calum Chambers ahead of the 2025/26 campaign.